That would be my guess. This quoted text is from their glossary of terms: “gage height–the height of the water surface above the gage datum (zero point). Gage height is often used interchangeably with the more general term, stage, although gage height is more appropriate when used with a gage reading.”
A buddy and I were going up to Rainy for the walleye run but we cancelled our trip due to below normal fishing and rising water levels. It sounds like the river is finally settling down. Good luck and have fun!